The world's largest confirmed impact crater is buried under South African farmland
About 2 billion years ago, an asteroid roughly 20-25km wide struck what's now South Africa, gouging a crater originally about 250km across. Erosion has worn it down to a faint ring of hills near the town of Vredefort, but it's still Earth's largest verified impact structure. It's now a UNESCO World Heritage Site studied for clues about the planet's early history.